EPON is a broadband access network offering multiple comprehensive services based on a high-speed Ethernet platform and the Time Division Multiplexer (TDM) Media Access Control (MAC) by applying point-to-multipoint network structure and passive optical fiber transmission. EPON comprises the central office device, namely Optical Line Terminal (OLT), the user-end device, namely Optical Network Unit (ONU), and a connection link, namely Optical Distribute Network (ODN).
In recent years, with large-scale application of EPON technology, how to develop controllable multicast service in EPON is a topic worthy studying.
The existing EPON multicast control method applies single-copy broadcast, the multicast service distribution control point is set in the ONU, and a multicast authority table is set in the OLT to control the authority of the multicast, and the illegal multicast data are filtered through setting the items in the multicast filter table in the ONU. For the ONU with several user ports, the snooping function in Internet Group Management Protocol (IGMP) has the multicast service only forwarded to the user ports which request the service. However, the OLT can only identify the ONU ID in the prior art, and for ONU with several user ports, only different ONUs can be distinguished in the multicast authority table saved in the OLT in the prior art, while different user ports in the ONU cannot be distinguished.
For example, when the ONU receives at user port 1 the IGMP message with address 224.1.1.1 for entering into the multicast, a conversion table is established by L2 Switch through the present snooping mechanism, and the information of user port 1 is recorded in the conversion table; the ONU forwards the IGMP message including the ONU ID and said multicast address for entering into the multicast to the OLT, the OLT searches the multicast authority table saved in itself, and returns OAM (Operation, Administration, Maintenance) frame including the VLAN ID (Virtual Local Area Network ID) of the multicast and IP address of the multicast to the ONU if it finds out that the ONU has the authority of multicast; the ONU adds the VLAN ID and the IP address of said multicast into the multicast filter table. The ONU forwards the multicast data to the user port 1 in the conversion table established by said snooping mechanism after receiving the multicast data of said multicast. When the IGMP message with multicast address 224.1.1.1 for entering into the multicast is received at user port 2 in the ONU, the ONU uses the snooping mechanism to record the user port 2 into said conversation table as well, and thus the user port 2 can receive the multicast data with multicast address 224.1.1.1.
From the above description, it can be seen that the existing multicast control method only performs multicast control for the ONU while not for different user ports in the same ONU, thus users without the multicast authority may also receive the multicast data. The existing multicast control method cannot implement accurate multicast control and has security vulnerability in technology.